Multiple opposed piston engine



Nov. 28, 1950 T. Y. KORSGREN 2,532,106

MULTIPLE OPPOSED PISTON ENGINE Filed Dec. 6, 1946 2 Sheets-Sheet l FLOW m PIPE ss 93 H 01. INF/P556 94 ROTATION OF SHAFT l4- THEODORE YNGVE KoRsGREN. Y

imam try/W Nov. 28, 1950 T. Y. KQRSGREN 2,532,106

MULTIPLE OPPOSED PISTON ENGINE Filed Dec. 6, 1946 2 Sheets-Sheet 2 v z 5 3 ZWFEZTZEF THEODORE YNGVE Kant an/v.

Patented Nov. 28, 1950 UNITED STATES PATENT OFFICE MULTIPLE OPPOSED PISTON ENGINE Theodore Yngve Korsgren, Winnetka, Ill.

Application December 6, 1946, SerialNo. 714,458

17 Claims. 1 My invention relates to'reciprocating engines of the type more generally described andclaimed in my copending application, Serial No. 714,457, filedDecember 6, 1946..

It is an object of my invention to provide an improved reciprocating engine;

A further object of my invention is to provide an improved reciprocating engine wherein two cycle operation is obtained withoutloss of fresh operating fiuid while at the same time good scavengi-ng of spent operating fluid isach-ieved.

Another object of my invention is to provide an improved reciprocating engine of the two cycle type having a fuel intake andexhaust system that is simple in construction and reliable in operation and avoids the need for valves.

It is yet another object of my invention to provide an improved reciprocating engine wherein the passages for operating fluid are self contained within the engine to the end that minimum size thereof is achieved. Still another object of my invention is to provide an improved reciprocating engine having a high degree of flexibility and efficiency which may be constructed to operate in either two cycle or four cycle fashion.

Still another object of my invention is to provide an improved reciprocating engine comprising a plurality of identical units to the end that mass production of a particular design of the elemental units maybe achievedand such numbers of them as are necessary to achieve a desired power output may be connected together to form a complete unit.

It is still another object of my invention to provide an improved reciprocating engine wherein periodic torque variations on the output shaft and on the support are minimized to the endthat high speedsmay be employed anda maximum output per unit volume achieved.

It is yet another object of my invention to provide an improved reciprocating engine having features of construction, combination, and arrangement, wherein. a high degree of simplicity in construction and reliability in operation is achieved, and which may be manufactured in an. inexpensive manner The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention, itself, however, both as to its organization and method of. operation, together with further objects and advantages thereofmay best be understood by reference to the following description.

taken. in connectionwith theaccompanying drawings.

On the drawings;

Figure I is a. partial cross-section view showing a single cylinder two cycle gasoline engine incorporating' the featuresof my invention;

Figure 2 is achart illustrating the operation of the engine of Figure 1;

Figure 3 isa partial cross-sectionalviewo-f an alternative embodiment of the engine of Figure 1;; and

Figure 4 is a partial cross secti'onal view of a multircylinder four cycleengine incorporating the features of my invention.

As shown on the drawings:

In Figure 1, l d represents the engine body or cylinder having cylindrical. cavity I2 formiugthe operating engine space. Shaft M is mounted within cavity 12 and is. supported at. its opposite ends by bearings-I 6 which are supported in turn by the end members I 8 attached to cylinder lll. Pistons 20- and 22 are shdably mounted within cavity H! in a manner to permit free sliding movement thereof relative tocylinder [0 and shaft [4, this mounting comprising bearings 24- which ride in groove 26 and 28 in shaft l4 and the pistons respectively. Pistons 20 and 1'2 are provided with inwardly extending angularl'y disposed recesses 30 and the inner races ofballbean ings 32 mounted thereon. The outer races of bearings 32 are limited to predetermined movements by bearings 38 which are supported in cylinder I0. Extensions-E0 on the outer race of bearings 32 provide a low friction engagement between bearings 38 and the outer races ofbearings 32. The effect of the engagementbetween extensions 4!! and bearings 38 is to prevent rotation of the outer races of bearings 32 and to cause these races to remain in. a plane passing through the centers of the respective bearings 38.

The operation of bearings 32 is to cause rotational movement of shaft 14 at uniform velocity to correspond with sinusoidal reciprocating movement of pistons 20. and 22. This operation is described in detail in my copending application, Application Serial No. 714,457, referred to above. Briefly, bearings32 permit translation of pistons 20.and22 relative toshaft [4' and cylinder Iii only by rotation of their outer races in the axis passing through the plane of the bearing and point 34 or 36. This rotation, however, requires corresponding rotation of the inner races ofthe bearings and the pistons 20 andZZ. Accordingly reciprocation of pistons wand v22 corresponds to rotation of shaft M. It can be shown that the reciprocation of pistons 28 and 22 corresponding to a constant angular velocity of shaft i6 is sinusoidal so that the pistons 28 and 22 execute simple harmonic motion as shaft M rotates at constant angular velocity.

In the engine of Figure 1, operating fluid is admitted through pipe 82 which is connected to intake ports 88 and and the carburetor shown generally at 88. When pistons 28 and 22 move to the closed position shown in Figure 1, a low fluid pressure exists in spaces 58 and 52 so that when ports E i and 88 are uncovered, air is forced by atmospheric pressure through pipe 82 to spaces and 52. Simultaneously, fluid is induced from carburetor 88 by the aspirator action of nozzle 54, this fluid mixing with the air to provide an explosive fluid-air mixture in chambers 58 and 52.

It is the function of pipe 58 to transfer the explosive fluid-air mixture from chambers 58 and 52 to operating chamber 58 located between pistons 20 and 22. This pipe connects ports 60, 82 and 84 of chambers 50, 52 and 58 respectively. Thus, when piston 22 moves to the right as seen in Figure 1 to the point wherein port 68 is unport 58, fluid from chamber 58 is enabled to pass through the pipe to the outer space, thereby perpressed explosive mixture in chamber 58 at the L proper point in the operating cycle. Voltage is applied to this spark plug from battery 12 by means of commutator 14 which is rotated by gear 16 and 18 in accord with the rotation of shaft [4. Commutator M is provided with a single conducting element 80 so that when shaft M has the angular position corresponding to maximum compression of the fluid in space 58, electrical energy is applied to Spark plug 10 to explode the mixture and produce power.

The operation of the engine of Figure 1 is as follows: When shaft It has the position shown in Figure 1, electrical energy is applied to spark plug 10 through commutator i4 and the compressed fluid-air mixture in space 58 ignited. Pistons 28 and 22 are then forced away from each other and rotational motion is imparted to shaft [4 by reason of bearings 32. As these pistons move, ports 54 and 58 are covered and the airgas mixture in chambers 58 and 52 compressed. Upon further motion of pistons 28 and 22 in accord with the pressures within space 58, ports 88 and 64 are covered, the former permitting egress of spent fluid from chamber 58 and the latter connecting chamber 58 with chambers 58 and 52. Since chambers 58 and 52 contain compressed fluid, fluid flow takes place through pipe 58 to recharge chamber 58 with the working medium. The inertia of shaft l2, together with the rotating parts connected thereto, causes the rotary motion thereof to continue after the power stroke and pistons 28 and 22 are caused to move towards the position of Figure 1. Ports 58 and 88 are then closed and the fiuid mixture within space 58 compressed. Simultaneously low pressure is produced in chambers 58 and 52 since there is no opportunity for fluid to pass thereto as ports 44, and 8% are covered. After a predetermined motion, ports as and 88 are uncovered and atmospheric pressure forces air through pipe 42 into spaces 50 and 52, carrying with it fuel from container 18. When the pistons reach the positions shown in Figure l, commutator M again connects spark plug 18 with battery '52 and a new explosion is initiated in chamber 58 to produce another power stroke and repeat the cycle.

One of the features of my invention resides in the improved performance of the engine of Figure 1 achieved by causing exhaust port 88 to close and open at earlier points in the cycle of operation than intake port 6 This is achieved by mounting piston 28 on shaft M with a slight degree of rotation relative to piston 22, thereby causing reciprocations of the former to lag reciprocations of the latter as the shaft rotates. The effect of this rotation will be evident from examination of Figure 2 which is a diagram illustrating the engine performance. In this diagram curve 82 shows the position of piston 20 along shaft it as a function of the rotation of that shaft. This curve is a sine wave by reason of the inherent operation of the mechanical movement comprising bearing 32 and bearing 38. Similarly, the motion of piston 22 as shaft [2 is rotated is shown by curve 8 2, this curve being displaced by the twist of piston 22 relative to piston 20. Each of the piston positions shown in Figure 2 is relative to the center point of cylinder I8, the line 86 indicating the maximum degree of approach of the pistons to that point. Line 88 indicates the position of ports 88 and 88 relative to the center of cylinder l8, whereas 98 indicates the maximum movement of the pistons. Since port 88 uncovers when piston 20 reaches the position thereof, this port opens at the point wherein line 88 crosses curve 82. As will be evident from Figure 2 this point corresponds to approximately rotation of shaft I i. At this point exhaust fluid flow takes place through pipe 68 as shown in curve 92. At about 210 rotation curve 82 again crosses line 88 and port 68 closes, thereby preventing further exhaust fluid flow in pipe 58 as indicated by curve 92.

Port 84 opens when piston 22 reache the position of port 84 as indicated by the point wherein curve 84 crosses line 88, Figure 2. As shown in the figure this point is at approximately 180 r0- tation of shaft M, as is indicated by curve 94. Intake fluid flow then takes place through pipe 56. This port is covered and fluid flow through pipe 56 discontinued when shaft I4 reaches approximately 240 as indicated by the point wherein curve 84 again crosses line 88.

From the above explanation it will be evident that port 58 is opened and closed at earlier points in the operating cycle than is port 84. In this manner the gases within space 58 which are under high pressure by reasons of the powerstroke are enabled to pass out through pipes 66 to a large extent before port 84 is opened. However, when port 64 is finally opened, port 88 is likewise open and fluid flow takes place in space 58 from port 64 to port 58, this fluid flow being due to the high pressure within spaces 58 and 52 and the low pressure at the outlet of pipe 66. This fluid flow is in a single direction through space 58, thereby causing the new working fluid to tend to occupy space 58 as the spent fluid passes therefrom. In this manner mixture of the two fluids is minimized and a maximum proportion of the spent fluid removed before the succeeding power stroke. In: addition, a minimum amount of fresh workingnuid passe from port 64 to port- 68 without undergoing a power stroke; Thisis a particularly important feature insofar as the efii-cienoy oi the engine of Figure 1 is concerned inasmuch as the improved scavenging and the reduced loss of fresh working fluid improves the efiicicncy of the engine as a whole and removes to a large degree the principal disadvantage of a two cycle engine, namely, poor scavenging.

The engine shownin Figure 3- is like that of Figure 1 except that shaft I4 has an internal passage. 96 which avoids the need for pipe 56, Figure 1. This passage opens into spaces 50' and 52 through ports 98 and I respectively, these ports corresponding to ports 60 and E2 in the engine or Figure l. Passage 95 further opens into space 5&by port I102 which corresponds to port Gkof the engine of Figure I; Operation-of the engine orEigure 3 is identical with that of Figure 1 except that fluid flow through passage 96 takes place instead 'of fluid flow through pipe 56.

Th engine of Figure 3 incorporates a modification of the fuel intake and exhaust system of the engine of Figure 1. In this modification, piston i 20 and 22 are given no rotation relative to each other as they are mounted on shaft It but port 68 is placed slightly closer to the center of the cylinder than: port 102. Hence port 68 opens atan earlier point in the cycle than port I02 and closes at a later point. Between the time port 68 is openedand port 102 opens, spent operating fluid passes out the former port from chamber 58 When port I02 subsequently opens, this action; continues but fresh fluid takes up the space formerly occupied by the spent fluid. After port I02 closes and port 68' remainsopen, the remaining. spent fluid passes from chamber 58 so that at the instant port 68 is closed the chamber is filled with fresh operating fluid One of the principal advantages of the mechanical movementused in the engine of Figure 1 to convert translational movement of piston 20 and 22' to rotational motion of shaft I4 is that it avoids the need for a crank shaft assembly, thereby making possible use of spaces 56' and 52. In the engine of Figure 1, this space is used as a precompression' chamber, which chamber produces a predetermined degree of compression of the operating fluid within spaces 50' and 52, the

amount of this compression being determined by the positioning of ports 44 and 46 and being controllable at will by choosing thelocations of these ports; However the utility of spaces 59 and 52 is not: limited to: their" use as precom-pression chainbers', but on the contrary they may be-used' as explosion chambers orfor such other purposes as are desirable. Figure 4 shows an engine wherein these spaces are used as explosion chamber for the working fluid and a four cycle operating cycle employed. In the engine shown in this figure, two separate units are provided, cylinder Illa containing' one unit and cylinder I 0b containing the other unit, Pistons 20a and 22a are mounted in cylinder Ma and on shaft Ma in the same manner as arepistons 20 and 22 of Figure 1. similarly'pistons 20b and 2'2b'a-re mounted on shaft Mb in the same manner as are pistons 20 and 22, Figure 1-. Bearings 32a and 32b cause rotational movement of shafts Ma and I do in accordance with the positions of pistons 20a, 22a and 20b and 2212, respectively. Shafts Ma" and Mb are connected against relative rotation by gears I04; I06 and I88; However, gears: we, Hi6- and I 08 are: ar

ranged so that pistons 20a and 22a are spaced relative to the center of cylinders Ilia at the same time that pistons 20b and 22b are positioned for minimum spacing cylinder Iflb, thereby causing alternate power strokes in cylinders Ido and "lb and achieving minimum variation the torques applied to gear I06.

Pipe I It! is a common intake pipe forcylind ers Illa and idly Fuel is supplied to spaces Silaand 52aof cylinder I011 from pipe Hit by valve H2 which opens into pipe lid which is in fluid cornmun-icationwith spaces 58a and 52a. Similarly, fluid from pipe I I 0 is admitted to space 580. of cylinder led by valve H6 which opens intopipe I I8. Valve i263, openinginto pipe I22, provides communication between pipe [It and spaces 5% and 52b of cylinder we, thereby providing for passage of fluid to these spaces; Valve IM-opens into pipe [26 toprovide'p-assage of working fluid into space 586 of cylinder 56b. Exhaust of spent working fluidfrom spaces 58a and is provided by valve I28 whereas-exhaust of spent fluid from space 58a is provided by valve" I32. Similarly valve I32 permitsexh-aust of spent working fluid from spaces 5% and 521101? cylinder it?) and valve I 34 permits passage of spent working fluid space 5% of cylinder I Eb. Camslt'iii are mounted to rotate with gear tilt and are shaped as described in further detailhereafter to provide the desired sequence of operation of valves H2, H6, I38, I28, 529, I25, 234 and 532.

Separate ignition systems are provided for each of the two units, comprisingthe engine of Figure 4. Ignition of working fluids in spaces 50a and 52a is provided by spark plugs I38 and I415 respectively, these spark plugs being supplied with electrical energy atthe proper time by battery I66 through commutator I. commutator IE4 is driven by gear I48 in correspondence with the motion of pistons Eliot and 2211. Similarly, spark plug Illa is provided with energy from battery I i-6 by commutator 14a. In the case of cylinder I db, spark plugs I49 and I 50 ignite the fluids within spaces 5% and 5219 when commutator I52 connects battery I54 thereto. Likewise the fluid Within space 58'?) is ignited by spark plug 'iflb'when the commutator 74b connects battery I5 3 "thereto. Cbmmutators Nb and I52 are rotated by gear E55 in accord with the positions of pistons 22b and" 22b.

The engine of Figure 4 operates as a 4 cycle engine but achieves the advantages of four cylinder operation by the novel combination of my invention. In the positions shown in the figure, a power stroke is being initiated in space 581) so as to cause motion of pistons 20b and 22b and rotate the shafts Nb and lid and the associated mechanism. In this condition valve I32 is open so that the resultant motion of pistons 20b and 22b will cause exhaust of working fluids from spaces Eiib and 52b. Simultaneously, pistons 20a and 22a commence their closing stroke, valve I i2 being open so that this stroke draws entrance of fresh working fluid to spaces 5M and 5202- and valves I38 and I I6 being closed to cause compres sion' of the fluid within space 58a. Fluid from container I58 is drawn into pipe I ID by the aspirator action of air drawn therethrough as pistons 2M and 22a move.

After shaft Ma and we have rotated to cause pistons 20b and 22b to be spaced and pistons 29a and 22a to be close together, a power stroke is initiated in space We bycornrnutator Ma, valve H2 closes to causethe succeeding motion of pistons 26a and 22a to compress the working fluid within spaces 59a and 52a, valve I34 opens to cause the successive closing stroke of pistons Zilb and 22b to exhaust spent working fluid from space 58b and valve I28 opens to cause ingress of fresh operating fluid to spaces and 52!). When the pistons have again reached the relative positions shown in Figure 4, valve I24 opens to cause the succeeding stroke to draw fresh fluid to space 5%, valve [2%) closes so that a succeeding stroke compresses the fluid in spaces 5% and 5217, a power stroke is initiated in spaces 59a and 52a by spark plugs [38 and H30 and valve I39 opens to permit exhaust from space 58a. Finally, after the pistons 26a and 22a become close together and pistons 28%) and 22b become separated, commutator I52 applies voltage from battery I56 to spark plugs Hi9 and I56 to cause power stroke of spaces 5% and 52b, valve E26 closes to cause compression within space 58b, valve H6 opens to cause passage of fresh operating fluid to space 58a and valve I28 opensto cause exhaust of fluid from spaces 552a and 5211. This stroke completes the cycle and further operation is merely repetition thereof.

From the above explanation it will be evident that the engine of Figure 4 operates as a four cycle engine having four cylinders and two power strokes for every cycle of rotation of shafts Ma and Mb. It will further be evident that the unbalanced application of torque incident to the cyclical operation of the engine is reduced greatly by the interconnection of the two cylinders whereby successive power strokes take place at uniform intervals of time.

It will be evident to those skilled in the art that the engine of Figure 4 represents only one of the many combinations that can be arranged using separate units consisting of cylinders having shafts extending therethrough and pistons connected to the shafts so that reciprocation of the pistons corresponds to rotation of the shafts. For example, the engine of Figure 4 might comprise two units similar to Figure 3 operating as two cycle units and avoiding the need for valves and a cam shaft. By interconnecting the two units so that power strokes take place at equal intervals of time, the output of the combined units is increased while at the same time the periodic torque variations are reduced in relative magnitude and doubled in frequency. It will be further evident to those skilled in the art that a standard unit engine may be arranged for mass production and these units combined to form engines of increased output, such as that shown in Figure 4, thereby providing the advantages of mass production methods while at the same time achieving a variety of useful engine designs.

While I have shown the particular embodiments of my invention, it will, of course, be understood that I do not wish to be limited thereto since many modifications both in the elements employed and their cooperative structure may be made without departing from the spirit and scope thereof. In particular the features thereof may be applied to Diesel engines and pump in addition to the gasoline engines shown and described. I, of course, contemplate by the appended claims to cover all such modifications as fall within the true spirit and scope of my invention.

I claim as my invention:

1. A reciprocating engine comprising in combination a first cylinder and a second cylinder, a pair of opposed pistons in each of said cylinders, a shaft in each of said cylinders, means connecting said pistons to said shafts to permit relative translational movement therebetween while restraining relative rotation thereof, means to cause said pistons to assume angular positions determined by their positions along said cylinders, means to close the free ends of said cylinders, means operable to cause successive power strokes in the spaces between said pistons and the spaces at the ends 0f said cylinders, the power strokes at the ends of each of said cylinders occurring simultaneously, and means connecting said shafts so that the total torque produced by the power strokes in said cylinders is exerted at a common point.

2. A reciprocating engine comprising in combination a first cylinder and a second cylinder, a pair of opposed pistons in each of said cylinders, a shaft in each of said cylinders, means connectin said pistons to said shafts to permit relative translational movement therebetween while restraining relative rotation thereof, means to cause said pistons to assume angular positions determined by their positions along said cylinders, means to close the free ends of said cylinders, means operable to cause successive power strokes in the spaces between said pistons and the spacesat the ends of said cylinders, the power strokes at the ends of each of said cylinders occurring simultaneously, and means connecting said shafts so that the total torque produced by the power strokes in said cylinders is exerted at a common point and successive power strokes occur thereon at equal increments of time.

3. A reciprocating engine comprising in combination a first cylinder and a second cylinder, pairs of opposed pistons mounted in said cylinders, shafts in said cylinders, means connecting said shafts to said pistons so that reciprocation of said pistons corresponds to rotation of said shafts, means closing the ends of said cylinders to define working spaces therein on both sides of each of said pistons, means operable to cause successive exhaust, intake compression, and power strokes in each of said spaces, as the corresponding shaft rotates, and means connecting said shafts so as to form a complete engine having recurrent power strokes separated by equal intervals of time.

4. A reciprocating engine comp-risin in combination a first cylinder and a second cylinder, pairs of opposed pistons mounted in said cylinders, shafts in said cylinders, means connecting said shafts to said pistons so that reciprocation of said pistons corresponds to rotation of said shafts, means closing the ends of said cylinders to define working spaces therein on both sides of the pistons, means operable to cause power strokes in said cylinders as the corresponding shaft rotates and means connecting said shafts so as to form a complete engine having recurrent power strokes after equal intervals of time.

5. A multi-cylinder reciprocating engine comprising a plurality of units, each unit comprising a cylinder having a pair of opposed pistons mounted on a common shaft and oppositely movable in periodic motion, and means coupling said pistons to said shafts to convert said periodic motion to rotation of said shaft; and means connecting said shafts so as to interconnect said units to apply to a common shaft the total torque produced.

6; A reciprocating engine comprising in combination a cylinder, 2. pair of opposed pistons in said cylinder, a shaft in said cylinder, means connecting said shaft to said pistons so as to cause rotation of said shaft in accord with the relative translational movement of said pistons, means closing the ends of said cylinder t define working spaces at the ends of said cylinder, a pair of exhaust valves and a pair of intake valves, means connecting one of said exhaust valves and one of said intake valves to cause successive intake, compression, power and exhaust strokes in the space between said pistons and means connecting the other of said exhaust valves and the other of said intake valves to cause successive and simultaneous intake, compression, power and exhaust strokes in the spaces at the ends of said cylinder, whereby a power stroke is produced for every cycle of reciprocation of said pistons.

7. A reciprocating engine comprising in co1nbination a cylinder, a pair of opposed pistons in said cylinder, a shaft in said cylinder, means to cause rotation of said shaft in accord with the translational movements of said pistons, said cylinder having an intake port and an exhaust port, said intake port being located towards one end of said cylinder to be uncovered b the stroke of one of said pistons and. said exhaust port being located towards the other end of said cylinder to be uncovered by the stroke of the other of said pistons, whereby intake fluid flow is in the same direction through said cylinder as exhaust fluid flow.

8. A reciprocating engine comprising in combination a cylinder, a pair of opposed pistons in said cylinder, a shaft in said cylinder, means to cause rotation of said shaft in accord with the translational movements of said pistons, said cylinder having an intake port and an exhaust port, said intake port being located towards one end of said cylinder to be uncovered by the stroke of one after and close before said exhaust port so as i to improv scavenging of spent fluid from said cylinder and intake of fresh fluid thereto.

9 A reciprocating engine comprising in combination a cylinder, a pair of opposed pistons in said cylinder, a shaft, means to cause rotation of said pistons and shaft upon translational movements of said pistons, said cylinder having an intake port and an exhaust port, said intake port being located on one side of the transverse center of said cylinder to be uncovered by one of said pistons and said exhaust port being located on the opposite side of the transverse center said cylinder to be uncovered by the other of said pistons, one of said pistons being arranged out of rotational phase with respect to the other so that said exhaust port closes and opens at earlier points in the cycle of rotation of said shaft than said intake port, whereby spent fluids are exhausted from said cylinder and fresh fluids supplied thereto with minimum loss in engine the reciprocation of the other, an intake port on one side of the transverse center line of saidcylinder to be uncovered by successive reciprocatons of said one piston, an exahust port on the opposite side of the transverse center line of said cylinder to be uncovered by successive reciprocations of said other piston, whereby fluid flow on intake to said cylinders is in the same direction as fluid flow on exhaust therefrom. and said exhaust port closes and opens at earlier points in the cycle of rotation of said shaft than said intake port.

11. A reciprocating engine comprising incombination a cylinder, a pair of opposed pistons in said cylinder, closures at the ends of said cylinder to define fluid tight spaces between the ends of said pistons and said closures, means providing a fluid passage from the ends of said cylinder near said closures to a point near one end of the space between said pistons when they have maximum relative spacing relative to each other, said cylinder having an exhaust port near the other end of said last mentioned space, and means operable to cause passage of working fluid to said first mentioned spaces, whereby working fluid is compressed in and passes from said first mentioned spaces, to the space between said pistons, to exhaust spent fluid through said exhaust passage, prior to combustion, upon successive strokes of said pistons.

12. A reciprocating engine comprising in combination a cylinder, a pair of opposed pistons in said cylinder, a closure at the end of said cylinder to define a fluid tight space between the end of one of said pistons and said closure, means providing a fluid passage from the end of said cylinder near said closure to a point near one means operable to cause passage of working fluid to said first mentioned space, whereby working fluid passes from said first mentioned space, to the space between said pistons, to scavenge spent fluid through said exhaust passage prior to final compression and combustion of said working fluid, upon successive strokes of said pistons.

' 13. A reciprocating engine comprising in combination, a cylinder, a pair of opposed pistons in said cylinder, closures on the ends of said cylinder to define fluid tight spaces between the ends of said pistons and said closures, means providing a fluid passage from the ends of said cylinder near said closures to a point near one end of the space between said pistons when said pistons have maximum spacing relative to each other, said cylinder having an exhaust port near the other end of said last mentioned space, said cylinder having intake ports to said first mentioned spaces, saidlast ports being located so as to be covered by said pistons when spaced relative to each other, a source of working fluid connected to said intake ports so that successive strokes of said pistons cause passage of said fluid to said first mentioned spaces, whereby said workend of one of said pistons and said closure, means providing a fluid passage from the end of said cylinder near said closure to a point near one end of the space between said pistons when said pistons have maximum spacing relative to each other, said cylinder having an exhaust port near the other end of said last mentioned space, said cylinder having an intake port to said first mentioned space, said last port being located so as tobe covered by said one piston when spaced relative to the other piston, a source of working fluid connected to said intake port so that successive strokes of said pistons cause passage of said fluid to said first mentioned space, whereby said working fluid passes from said first mentioned space, to: the space between said pistons to scavenge spent fluid through said exhaust passage prior to final compression and combustion of said working fluid upon successive strokes of said pistons.

15. A reciprocating engine comprising in combination a cylinder, a pair of opposed pistons in said cylinder, a shaft in said cylinder, means connecting said shaft and said pistons to cause said cylinder having intake ports to said first mentioned spaces, said ports being located so as to be covered by said pistons when spaced relative to each other, a source of working fluid connected to said intake ports so that successive strokes of said piston cause said working fluid to pass to said first mentioned spaces, whereby working fluid passes from said first mentioned spaces through the space between said pistons -to said exhaust passage upon successive strokes of said pistons.

16. A reciprocating engine comprising a. cylinder, a pair of opposed pistons in said cylinder,

closures for the ends of said cylinder, a shaft passing through said cylinder, means to cause successive relative reciprocatory movements of said pistons, said shaft having a passageway with openings to the spaces between said pistons and said closures and one end of the space between said pistons when they have maximum spacing relative to each other, said cylinder having an exhaust port at the other end of said last mentioned space, and means to admit working fluid to said first mentioned spaces whereby said fluid passes from said first mentioned space to said last mentioned space and out said exhaust port upon successive strokes of said piston.

17. A reciprocating engine comprising in combination a cylinder, a pair of opposed pistons in said cylinder, a shaft, means to cause rotation of said shaft in accord with the translational and rotational movements of said pistons, said cylinder having an intake port and an exhaust port, said intake port being located on one side of the transverse centerline of said cylinder and said exhaust port being located on the opposite side of the transverse centerline of said cylinder, said intake port being uncovered by one of said pistons and said exhaust port being uncovered by the other of said pistons, and said piston covering said exhaust port being angularly displaced with respect to said piston covering said intake port, to effect opening of said exhaust port prio to opening of said intake port.

THEODORE YNGVE KORSGREN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 667,298 Cunningham Feb. 5, 1901 1,106,043 Hallett Aug. 4, 1914 1,324,520 Robbins Dec. 9, 1919 1,629,686 Dreisbach May 24, 1927 1,693,024 Drummond Nov. 27, 1928 1,876,506 Lee Sept. 6, 1932 1,976,286 Kreidler Oct. 9, 1934 2,079,289 Janicke May 4, 1937 2,246,701 Steiner June 24, 1941 2,316,394 Bovee Apr. 13, 1943 FOREIGN PATENTS Number Country Date 524,942 Germany of 1931 

